How do I tell hex from a hash?

By length and by whether it decodes to readable text. Hashes are fixed-length (32, 40, 64, 128 hex characters) and decode to noise. If your hex is one of those lengths, identify it as a hash first.

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Hex to text converter

Convert hexadecimal to text and back, tolerating whitespace, commas, and `0x` prefixes. Runs entirely in your browser.

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Hex writes each byte as two characters from 0-9a-f. It is the lingua franca of everything binary: hashes, keys, packet dumps, magic bytes, memory addresses. Unlike Base64 it is easy to read at a glance, which is exactly why it shows up whenever a challenge wants you to see the bytes rather than hide them.

How to recognise it

Only 0-9, a-f, A-F, and the length is even. Any g-z rules it out immediately.
Common decorations: 0x prefixes, \x escapes, space or colon separators (de:ad:be:ef), and line-wrapped dumps.
A bare 32/40/64-character hex string is almost certainly a hash - send it to the hash identifier rather than decoding it as text.

Hex is also the format in which people make transcription mistakes, because a dropped character shifts every byte after it by half a byte and produces output that is uniformly wrong rather than locally wrong. An odd-length hex string is always a copy-paste error, never a valid encoding - if a decode fails on the length, count the characters before looking for an exotic variant.

Length tells you a lot

Hex characters	Bytes	Likely meaning
32	16	MD5, or an AES-128 key/IV
40	20	SHA-1, or a Git object hash
64	32	SHA-256, or an AES-256 key
128	64	SHA-512

Before decoding hex as text, check whether the length is a digest length.

Worked example

Hex with 0x prefixes

Input

0x70 0x69 0x63 0x6f 0x43 0x54 0x46 0x7b 0x68 0x33 0x78 0x5f 0x69 0x73 0x5f 0x66 0x75 0x6e 0x7d

Result

picoCTF{h3x_is_fun}

Prefixed and space-separated, the way a disassembler prints it. The `0x` markers are noise, not data, and come off before the decode.

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Common questions

How do I tell hex from a hash?: By length and by whether it decodes to readable text. Hashes are fixed-length (32, 40, 64, 128 hex characters) and decode to noise. If your hex is one of those lengths, identify it as a hash first.

Part of a module

1. Recognising encodings

Tell Base64 from hex from Base32 from binary on sight, peel layered encodings, and learn why an encoding is not encryption.

Practise on real challenges

Go deeper

Spot the encoding: reading base64, base32, hex and friends at a glanceAlphabet, length, and padding are enough to name almost any encoding on sight. A field guide to the encodings CTFs actually use, the magic prefixes that tell you what is underneath, and the traps that make a correct guess look wrong.